In recent years, product appeal (product power) has been further requested for industrial products, particularly for automobiles. The product appeal is a quality of appearance and the design image of a paint color lies in the quality.
In the process of an automobile design, a designer of an automobile decides the paint color, and then it is necessary to accurately communicate the design image of a paint color along the concept of the type of an automobile designed by the designer to a designer of the paint maker for manufacturing paints.
When a paint color is a solid color having no directional property, a designer of an automobile can accurately communicate the design image of a paint color to a paint maker by using various color sample books in common. However, because a metallic color which changes color depending on the viewing angle is not included in color sample books, a designer of an automobile may use an image picture as a communication tool. The image picture shows the image of a paint color as one picture along the concept of the type of an automobile to which a designer of an automobile applies a paint color.
A specific example of the image picture is the underwater photo shown in FIG. 2. This photograph, which looksup at the sea surface from the seabed, expresses a change of colors from the blue of redness with low brightness up to the blue of yellowness with a high brightness. To embody these images as paint colors, a designer at a paint company designs a paint color in accordance with their experience and know-how.
Thus, various pictures are used as image pictures. However, to develop a paint color by understanding images obtained as paint colors from those pictures, a designer must search a color stored in the designer's brain which was experienced in the past out of colors in a specified plurality of regions in the pictures in accordance with their highlight and shade colors. This search requires years of experience and craftsmanship in order to understand a picture of a designer of an automobile and prepare the paint color having a color tone the same as the picture.
As a case of searching a color from RGB values of a point specified in a digital picture, Japanese Patent Application Publication No. 121558/1995 discloses a technique for obtaining RGB values from a specific point in a display means for displaying a picture, searching a data holding means and simply obtaining the name of the color. However, a method for searching a color changes with the viewing angle.
Moreover, Japanese Patent Application Publication No. 269411/1999 discloses a technique in which RGB values from a computer graphics picture are acquired and converted into tri-stimulus value, an approximated color is searched from the database with which the tri-stimulus value of a plurality of paint formulations is stored, and a technique of asking for paint formulation by CCM is indicated. However, this technique requires previous measurement and calculation in order to convert RGB values into XYZ of a color measurement value. Therefore, it is necessary to previously prepare color characteristics of the device used (digital camera, scanner, and monitor) (they are referred to as color profiles) and an immense amount of time is required. Moreover, when a reflectance exceeds 100% (white solid), such as a high-brightness and high-chroma metallic paint color, the brightness (value Y of XYZ or L* of L*a*b*) exceeds 100. However, in the case of the digital gradation of a monitor that is generally used, values to be taken for each channel of RGB values are integers of 0 to 255. Therefore, a dynamic range is very narrow compared to the brightness of a color measurement value. Therefore, to estimate a high-brightness high-chroma metallic paint color having a wide dynamic range from RGB values having a narrow dynamic range, a desired paint color may not be obtained because a large error occurs.
The following two Japanese documents are representative of the background of the present invention:
(1) “Tanoshiku manabu JAVA di hajimeru gazo shori programming” (Picture processing programming started with merrily learning JAVA) by Mikio Sugiyama, issued by Kabushiki Kaisha D ART, Dec. 20, 2002, pp. 144-150; and
(2) “Shin JAVA gengo nyumon/Senior hen” (New Java language guide/senior edition) by Haruhiko Hayashi, issued by SOFTBANK Publishing Inc., Mar. 20, 2002, pp. 542-543.
It is an object of the present invention to provide a method for specifying a paint color of an industrial product, particularly a metallic paint color having a high design characteristic from a digital image picture for showing the quality sense of a color exhibited by a customer.